Compounds of structural formula I ##STR2## are known to be carbonic anhydrase inhibitors useful in the treatment of ocular hypertension and glaucoma by topical ocular administration, as disclosed by Baldwin et al. in U.S. Pat. No. 4,677,115 (1987) the disclosure of which is incorporated herein by reference.
It has been found that the dextro-or S(+)-enantiomer of I wherein R is isobutyl and Y is sulfur manifests most of the activity found in the racemate. Accordingly, the levo-enantiomer being of no use would be discarded. Now, however, with the present invention, there is provided a means of utilizing the levo-enantiomer by racemizing it followed by resolution of the racemate to produce additional dextro-enantiomer. The resulting levo-enantiomer may, of course, be recycled through additional racemizations/resolutions.
It is an object of this invention to provide a process for racemization of the pharmacologically less active enantiomer of Compound I.
It is a further object of this invention to provide a process to increase the effective synthetic yield of the more useful enantiomer of Compound I.